TISSUES Body Tissues Cells are specialized for particular

TISSUES

Body Tissues § Cells are specialized for particular functions § Tissues - groups of cells with similar structure and function § Histology - study of the organization of cells and extracellular material into tissues and organs § Four primary tissue types § 1) Epithelium 2) Connective tissue 3)Nervous tissue 4) Muscle

Epithelial Tissues § Found in different areas § 1) Body coverings § 2 ) Body linings § 3) Glandular tissue § Functions § 1) Protection § 2) Absorption § 3) Filtration § 4) Secretion

Epithelium Characteristics § 1) Cells fit close together – Desmosomes and Tight junctions § 2) Apical Surface - Tissue layer always has one free surface (unattached) exposed to the body’s surface or the cavity of an internal organ § 3) The lower surface is bound by a basement membrane § 4) Avascular (have no blood supply) so they depend on diffusion for food and oxygen § 5) Regenerate easily if well nourished

Classification of Epithelium § Each Epithelium is given 2 names: § First name indicates the Number of cell layers § Simple – one layer § Stratified – more than one layer Figure 3. 17 a

Classification of Epithelium § Second name indicates the Shape of cells § Squamous – flattened § Cuboidal – cubeshaped § Columnar – column-like Figure 3. 17 b

Simple Epithelium § Simple squamous § Single layer of flat cells resting on a basement membrane § Cells fit closely together. § Forms membranes where filtration or exchange of substances through rapid diffusion occurs § Ex: Serous membranes that line organs and air sacs in lungs Figure 3. 18 a

Simple Epithelium § Simple cuboidal § Single layer of cubelike cells on basement membrane § Common in glands and their ducts § Forms walls of kidney tubules and covers the ovaries Figure 3. 18 b

Simple Epithelium § Simple columnar § Single layer of tall cells that fit closely together § Often includes goblet cells, which produce mucus § Lines entire digestive tract § Functions in absorption and secretion Figure 3. 18 c

Simple Epithelium § Pseudostratified Columnar § Single layer, but some cells are shorter than others ALL cells touch basement membrane § Often looks like a double cell layer § Sometimes ciliated, such as in the respiratory tract § May function in absorption or secretion § Also has goblet cells to produce mucous Figure 3. 18 d

Stratified Epithelium § Stratified squamous § Cells at the free edge are flattened; cells near the basement membrane are cube or column shaped § Found as a protective covering where friction is common Figure 3. 18 e

Stratified Epithelium § Stratified squamous (continued) § Two types: § 1) SS Keratinized – all extenal skin § Keratin is a protein that makes skin dry and rough and keeps water out and things like bacteria and viruses. § Keratin doesn’t allow you to see the nucleus and it will be flaky § 2) SS Non-Keratinized – all internal skin Mouth, tongue, vagina § No keratin so the nucleus can be seen to surface layer; still able to resist penetration of organisms but skin is moist & slippery (resists wear & tear) Figure 3. 18 e

Stratified Epithelium § Stratified cuboidal and columnar § 1) Rare in human body § 2) Found mainly in ducts of large glands

Stratified Epithelium § Transitional epithelium - Highly modified, stratified squamous epithelium § Shape of cells depends upon the amount of stretching § 1) Basal layer cells (bottom) are cuboidal or columnar § 2) Free (apical) surface cells are rounded and dome like if not stretched but squamous like (flat) when full of urine § Lines organs of the urinary system (Ureters and Bladder) Figure 3. 18 f

Glandular Epithelium § Gland – one or more cells that secretes a particular product § Two major gland types § Endocrine gland – Ductless and the secretions are hormones § Exocrine gland - Empty through ducts to the epithelial surface. § Include sweat and oil glands

Connective Tissue § Found everywhere in the body § Includes the most abundant and widely distributed tissues § Functions: 1) Binds body tissues together 2) Supports the body 3) Provides protection

Connective Tissue Characteristics § Variations in blood supply § Some tissue types are well vascularized (much blood supply) Ex: bone § Some have poor blood supply (tendons or ligaments) or are avascular (no blood) (cartilage) § Extracellular matrix – main difference between other tissue types § Non-living material that surrounds living cells